There are now six life stages: baby, toddler, child, teenager, adult, and elder. An additional young adult stage is added when you get the University expansion pack. Sims can now grow up and eventually die. In the first game, Sims would stay children forever and adults would stay adults forever. Teenagers can hold jobs as well as go to school.

Careers have gone under many changes. There is now a schedule; there are seven days in a week, and Sims at school are off on Saturday and Sunday. Sims can now get paid vacation days and start working 4–5 days a week. A meter measures job performance (their mood when they get to work). A new thing called "chance cards" lets the player pick what to do in a situation. Sims can gain/lose skill points, gain/lose money, or be promoted, demoted, or even fired.

Children and teenagers now bring homework home and their grades rise or fall depending on whether they finish it or not. Teenagers can hold jobs as well as go to school, but if their grades drop too low they can lose their job.

Other new things are wants and fears. These change when a want or fear is done or when the Sim wakes up from sleep.

Also, Sims can have aspirations (big things they want to do) like to have a family, to have many friends, to fall in love, to learn a lot, or to have a lot of money. A player can choose which aspiration they want their Sim to have, and the aspirations will affect their wants and fears. For example, a Sim with the family aspiration might want to have a child, but a Sim with the money aspiration might want to get a job instead.

Like in the first Sims game, a mother Sim and a father Sim can have a child. Also, children can be made at the start of the game or got from the adoption service.

One of the biggest changes in Sims 2 is that a Sim can go to a community lot (a place in the town like a store or a park). They can go there by using the phone to call a taxi.